Which is better iron or aluminum heads?

 

iron heads flow better out of the box but aluminum heads can be 'worked over' better.

 

this has been talked about alot. do a search

 

Factory to factory, ported to ported, iron heads will flow marginally more than aluminum, but NOT enough to offset the negative impact the extra weight over the nose.

 

Aluminum. 50 lbs less weight. You can run a point higher compression. Aluminum can be ported to flow much more than untouched iron heads if you want to offset the difference.

 

I'm guessing Dwayne will be in here before too long to set the record straight

 

Aluminum REQUIRES more compression than iron this is die to it pumping heat into the cooling system where it is waste. I love how people say it "allows" more compression, you have to run more just to get the same power due to the lesser thermal efficiency. On the weight, a source I trust more than 98% of the rest of this forum pegs the difference at closer to 35#. If someone wants to get me an ACCURATE weight of one aluminum head I can weight an iron on an accurate scale at work, I don't want any bathroom scale stuff here.

The aluminums do have an advantage not being touched on here and one that is nice for perfomance use, they have screwin studs to begin with where the iron have pressed which should be removed and tapped for screwin. If you are building a boosted motor or a stroker the larger chamber of the iron may help keep compression in check while allowing you to still run a thin gasket for good quench. The iron head motors having head gasket problems is almost unheard of at least compared even to the low number of aluminum head motors that do.

 

Do I win some sort of prize?

 

Yeah, iron is just what I want to run for a performance head! More ballast for the front! If you've gotta boat like a Caprice I guess it doesn't matter too much.

FTR, my sincerest heartfelt apologies on the inaccuracies of the weight, the difference in weight is almost exactly 44 pounds if you compare two (2) small block Chevrolet cast iron heads to two (2) small block Chevrolet cast aluminum heads.

Thought I would make a quick post stating basic points...

 

Aluminum is "prettier".

 

And it doesnt rust

 

I do not claim iron is always best just think the ignorance surrounding it should be corrected not propogated. As far as the weight say your f-body is 3800lbs. reasonable right, so let's go with the 50# number so that is about 1.3% really earth shattering huh. As far as rust sure aluminum corrodes it just corrodes white not the drastic color change you get with iron.

As far as smallblock heads how about we get this right, someone has to have a set of preferably unported aluminums around watingin to be ported just like my spare irons are, I will go throw one in the car right now, I will also look up the casting number to see if it is a 94-5 or a 96 and ask whomever posts aluminum specs to do the same as it is generally acepted there are the earlier thicker aluinums and the later thinner but higher flowing as cast aluinums. I will use the scale we use for smallpackage shipping at work, I am unsure of when it's last calibration was but we check it against our larger freight scale and they agree so it is at least close it will give me ouces too.

1996LT1NY, no prize just pride in knowing you helped get information straight even if I am wrong I want ACCURATE numbers made public, all the info thrown around here is pointless if it is wrong so let's just make sure we get it all right.

 

I really wanted to win something





Anyhow.. I just weighed (since were on the topic of accuracy there is no "t" in weigh or weighed ) a 1993 LT1 head. There are no valve springs on it, but the stock valves are present. The 93 head came in at 20lbs 3 oz.

I also weighed one of my AFR 190 CNC'd heads with valve springs on it (1.55") & the AFR came in at 29lbs exactly. Thats right.. the AFR head is almost 50% heavier !

Now we will weight & oops wait & see what you iron heads weigh & will have a fairly correct comparison

It will be pretty cool to have some sort of definitive information on the weight difference between the two types of heads.

 

I'm not gonna type it again. See above for weight difference. I didn't type it because I needed the practice. I'm sure this could vary by a few ounces given porting.

Observe these sentences:

1. Aluminum heads can be run a point higher in CR compared to iron.

2. Aluminum heads should be run a point higher in CR compared to iron.

Semantics. I could've chosen either of these sentences. I am well aware of the differences of running aluminum heads vs. cast iron heads considering thermal efficiency. I just chose sentence #1.

I just can't believe that someone is actually DEFENDING the use of iron over aluminum for PERFORMANCE!! In no way, for strictly performance, is cast iron a logical answer to the original question.

Speed is all about the tried and true power to weight ratio. This is a concept very familiar with ANYONE involved in any type of racing. They are CONSTANTLY calculating these figures for a reason. Guess what? It applies to street cars too.

If you are involved in any kind of racing, focusing solely on power is the biggest mistake that can be made. There should be a constant thought process on weight reduction as this can give a big advantage to a car that can be misconceived as heavy by the competition. Thought processes like "that's only 1.3%" will lose you races. 44 lbs in a car like mine is alot of weight!

For any given power, the less weight, the faster you go. Its that simple.

I'm not in any way saying that no one should ever use cast iron heads. They are out there in large numbers, and if working within a budget, they fit the bill. But with finances aside, aluminum is ALWAYS the choice for performance. Period.

Sorry for the lecture kids. Just getting the "information straight"

 

Iron is thermally more efficient and the heads have slightly better ports.

96capricemgr- My f-body weighs 3400 lbs and I think you discredit weight too much. Many people spend lots of money trying to reduce less weight than that. Tubular cross members and suspension components, FRP hoods, etc.

You can port even the stock aluminum heads to support lots of power, you can use higher compression to negate the thermal effeciency, and still save the weight. I would never use iron heads. You could certainly make a fast car with iron heads, just not many people would choose to especially when they already have aluminum.